Radiation curable resin composition

ABSTRACT

The present invention provides a curable composition, comprising: a (meth)acrylate urethane compound derived from a polypropylene glycol or a propyleneoxide ethyleneoxide copolymer glycol having a molecular weight between 1,000 and 13,000 and an amount of unsaturation less than 0.01 meq/g. The liquid curable resin composition of the present invention has improved liquid stability and can produce cured products having superior mechanical characteristics by polymerization. The composition further comprises preferably a primary or secondary amine. The liquid curable resin composition can be used as a coating material for optical fibers, adhesives, and the like. The composition is particularly suitable as a coating material for optical fibers for which long-term stability is required.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims the benefit of Provisional Application60/145,294 which was filed on Jul. 23, 1999.

FIELD OF THE INVENTION

The present invention relates to a curable composition having high speedcuring and capable of producing cured products by polymerization withoutimpairing mechanical properties. In particular, the curable compositionof the present invention is a liquid curable composition that can beformulated for use in a wide variety of applications including, forexample, coatings and/or binders. In particular, these curablecompositions offer relatively fast cure speeds that offer advantages inmany application such as in the production of fiber optics whereinproduction speeds make it desirable to utilize primary coatings,secondary coatings (including, for example transparent and/or coloredsecondary coatings), inks, matrix materials and/or bundling materialsthat can be cured rapidly.

BACKGROUND OF THE INVENTION

In the production of optical fibers, a resin coating is appliedimmediately after spinning molten glass fibers for protection andreinforcement. A known structure of the resin coating has been adouble-layered coating structure consisting of a primary coating layerof a flexible resin which is coated on the surface of optical fibers anda secondary coating layer of a rigid resin which is provided over theprimary coating layer. A so-called optical fiber ribbon has been knownin the art in the application of optical fibers provided with such aresin coating. The optical fiber ribbon is made from several opticalfibers, e.g., four or eight optical fibers, arranged on a plane andsecured with a binder to produce a ribbon structure having a rectangularcross section. A resin composition for forming the primary coating layeris called a soft coating, a resin composition for forming the secondarycoating layer is called a hard coating, and a material for bindingseveral optical fibers to produce the optical fiber ribbon structure iscalled a ribbon matrix material. Often, the fibers for identificationpurposes will be further coated with an ink, which is a curable resincomprising a colorant (such as a pigment and/or a dye), or the secondarycoating may be a colored secondary coating (i.e, comprise a colorant).In addition, a material for the further binding of several optical fiberribbons to produce multi-core optical fiber ribbons is called a bundlingmaterial.

Characteristics required for curable resins used as coating materialsfor optical fibers include: being a liquid at room temperature andhaving a sufficiently low viscosity for excellent coating; exhibitingsuperior storage stability and no compositional distribution as aliquid; providing good productivity owing to a high cure speed; havingsufficient strength and superior flexibility after curing; exhibitingvery little physical change during wide range temperature changes, inparticular primary coatings should have very low Tg; having superiorheat resistance and superior resistance to hydrolysis; showing superiorlong term reliability due to little physical change over time; showingsuperior resistance to chemicals such as acids and alkalis; absorbingonly a small amount of moisture and water; exhibiting superior lightresistance; exhibiting high oil resistance; producing little hydrogengas which adversely affects optical fibers; and the like.

In the production of optical fibers and optical fiber assemblies, one ofthe limitations on how fast the production line can be operated is thecure speed of the coatings and/or binder. Accordingly, it is desirableto develop coatings and/or binders with faster cure speed.

The resin composition for coating optical fibers must remain a liquidduring production of the coating, and after being stored for a longperiod of time. If the resin composition solidifies entirely orpartially during storage by (e.g.) flocculation or crystallization, thecomposition must be heated to avoid any problems in the coating processof the optical fibers, thereby impairing handling of the resincomposition.

An object of the present invention is to provide a liquid curable resincomposition which exhibits a faster cure speed and better agingcharacteristics, for example, lower yellowing of the cured composition.A further object of the present invention is to provide coatings havinga low Tg (glass transition-temperature).

SUMMARY OF THE INVENTION

The present invention provides a curable composition, comprising: a(meth)acrylate urethane compound derived from a polypropylene glycol ora copolymer comprising propyleneoxide and ethyleneoxide (herein afteralso just named polypropyleneglycol) having a molecular weight between1,000 and 13,000 and an amount of unsaturation less than 0.01 meq/g,and/or mixtures of (meth)acrylate urethane compounds derived from such apolypropylene glycol and other polyols. The liquid curable resincomposition of the present invention has improved liquid stability, andimproved cure speed; the cured products have superior mechanicalcharacteristics. The liquid curable resin composition can be used as acoating material for optical fibers, adhesives, and the like. Thecomposition is particularly suitable as a coating material for opticalfibers for which long-term stability is required. Also, the compositioncan be formulated to achieve low Tg, e.g. between −70° C. and −30° C.

In particular, the compositions of the present invention offerrelatively fast cure speeds which offer advantages in many applications,including the production of fiber optics wherein production speeds makeit desirable to utilize primary coatings, secondary coatings (including,for example transparent and/or colored secondary coatings), inks, matrixmaterials and/or bundling materials that can be cured rapidly.

Furthermore, the present invention provides a method for forming thecurable composition of the present invention comprising a process forforming the urethane compound by reacting

(a.1) a polypropylene glycol or a polypropylene/ethylene glycolcopolymer having a molecular weight between 1,000 and 13,000 and anamount of unsaturation less than 0.01 meq/g, and

(a.2) optionally, a further polyol or mixture of polyols;

(b) a polyisocyanate, and

(c) a (meth)acrylate containing a hydroxyl group, wherein the processincludes (i) reacting said glycol (a.1 and if applicable a.2), thepolyisocyanate, and the hydroxyl group-containing (meth)acrylatealtogether; (ii) reacting said glycol and the polyisocyanate, andreacting the resulting product with the hydroxyl group-containing(meth)acrylate; (iii) reacting the polyisocyanate and the hydroxylgroup-containing (meth)acrylate, and reacting the resulting product withsaid glycol; or (iv) reacting the polyisocyanate and the hydroxylgroup-containing (meth)acrylate, reacting the resulting product withsaid glycol, and reacting the hydroxyl group-containing (meth)acrylateonce more.

In a further aspect of the invention, a radiation curable resin isprovided, for a primary coating of an optical fiber comprising (a) 40-95wt % of polyurethane having a polyoxyalkylene structure, in which theweight ratio of propylene oxide and ethylene oxide is 100:0 to 80:20,and an ethylenically unsaturated group, (b) 3-50 wt % of mono-functional(meth)acrylate of which the homopolymer has a glass transitiontemperature of 20° C. or less, and (c) 0.01-5 wt % of primary orsecondary amine compound, wherein wt % is based on the total amount ofthe components (a), (b), and (c).

A DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(Meth)acrylic—as used herein is understood to represent separately andcollectively acrylic, methacrylic and mixtures thereof. Similarly,(meth)acrylate as used herein is understood to represent separately andcollectively acrylate, (meth)acrylate, and mixtures thereof.

Polypropylene glycol or polypropylene/ethylene copolymer glycol (havinga specified molecular weight and a specified amount of unsaturation)—asused herein is understood to refer to a polypropylene glycol comprisingcomposition having a plurality of polypropylene glycol moieties andoptionally ethylene glycol moieties that on average have the statedmolecular weight and the stated unsaturation (referred to the meq/gunsaturation for the total composition, which is typically less than0.01 meq/g).

The curable resin of the present invention comprises a urethane compoundhaving at least one (meth)acrylate group derived from a polypropyleneglycol or polypropylene/ethylene copolymer glycol having a molecularweight between 1,000 and 13,000, and preferably between 2,000 and 8,000,and an amount of unsaturation less than 0.01 meq/g, and preferablybetween 0.0001 and 0.009 meq/g and, optionally, mixtures ofpolypropylene glycol or polypropylene/ethylene copolymer glycol with atleast one additional polyol. Polypropylene glycol orpolypropylene/ethylene copolymer glycol includes 1,2-polypropyleneglycol, 1,3-polypropylene glycol and mixtures thereof, with1,2-polypropylene glycol being preferred, and copolymers ofpropyleneoxide and ethyleneoxide in the weight ratio of 100/0 to 70/30.The copolymer may comprise ethyleneoxide blocks. Preferably, the weightratio is 100/0-80/20 propyleneoxide/ethyleneoxide. Suitablepolypropyleneglycol homo- or copolymers are commercially available underthe trade names of, for example, ACCLAIM 2200, 3201, 4200, 6300, 8200,2220,4220 (manufactured by Lyondell), Preminol X-602, X-603, PML-3005,PML-30130, PML-3012, PML-4002, PML4010, PML-5001, PML-5005, PML-7001,PML-7003, PML7005, PML-70012 (manufactured by Asahi Glass Co., Ltd.),and the like. All these compounds have an unsaturated group content of0.01 meq/g or less. Such urethane compounds may be formed by anyreaction technique suitable for such purpose.

The urethane (meth)acrylate can be prepared by reacting

(A1) the polypropylene glycol or polypropylene/ethylene copolymerglycol, and optionally,

(A2) a further polyol or mixture of further polyols;

(B) a polyisocyanate, and

(C) a (meth)acrylate containing a hydroxyl group.

Given as examples of the process for manufacturing the urethane(meth)acrylate by reacting these compounds are (i) a process forreacting the glycol (or mixture of the glycol with at least one furtherpolyol (A2)), the polyisocyanate, and the hydroxyl group-containing(meth)acrylate altogether; (ii) a process for reacting the glycol andthe polyisocyanate, and reacting the resulting product with the hydroxylgroup-containing (meth)acrylate; (iii) a process for reacting thepolyisocyanate and the hydroxyl group-containing (meth)acrylate, andreacting the resulting product with the glycol; and (iv) a process forreacting the polyisocyanate and the hydroxyl group-containing(meth)acrylate, reacting the resulting product with the glycol, andreacting the hydroxyl group-containing (meth)acrylate once more.

Given as examples of further polyols contributing further polymericunits that may be suitable as component (A2) are polyether polyols,polyester polyols, polycarbonate polyols, polycaprolactone polyols, andother polyols. These polyols may be used either individually or incombinations of two or more. There are no specific limitations to themanner of polymerization of the structural units in these polyols. Anyof random polymerization, block polymerization, or graft polymerizationis acceptable.

Given as examples of the polyether polyols are polyethylene glycol,other polypropylene glycol, other polypropylene glycol- ethyleneglycolcopolymer, polytetramethylene glycol, polyhexamethylene glycol,polyheptamethylene glycol, polydecamethylene glycol, and polyether diolsobtained by ring-opening copolymerization of two or moreion-polymerizable cyclic compounds. Here, given as examples of theion-polymerizable cyclic compounds are cyclic ethers such as ethyleneoxide, isobutene oxide, tetrahydrofuran, 2-methyltetrahydrofuran,3-methyltetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexeneoxide, styrene oxide, epichlorohydrin, isoprene monoxide, vinyl oxetane,vinyl tetrahydrofuran, vinyl cyclohexene oxide, phenyl glycidyl ether,butyl glycidyl ether, and glycidyl benzoate. Specific examples ofcombinations of two or more ion-polymerizable cyclic compounds includecombinations for producing a binary copolymer such as tetrahydrofuranand 2-methyltetrahydrofuran, tetrahydrofuran and3-methyltetrahydrofuran, and tetrahydrofuran and ethylene oxide; andcombinations for producing a ternary copolymer such as a combination oftetrahydrofuran, 2-methyltetrahydrofuran, and ethylene oxide, acombination of tetrahydrofuran, butene-1-oxide, and ethylene oxide, andthe like. The ring-opening copolymers of these ion-polymerizable cycliccompounds may be either random copolymers or block copolymers.

Included in these polyether polyols are products commercially availableunder the trademarks, for example, PTMG1000, PTMG2000 (manufactured byMitsubishi Chemical Corp.), PEG#1000 (manufactured by Nippon Oil andFats Co., Ltd.), PTG650 (SN), PTG1000 (SN), PTG2000 (SN), PTG3000,PTGL1000, PTGL2000 (manufactured by Hodogaya Chemical Co., Ltd.),PEG400, PEG600, PEG1000, PEG1500, PEG2000, PEG4000, PEG6000(manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and Pluronics (byBASF).

Polyester diols obtained by reacting a polyhydric alcohol and apolybasic acid are given as examples of the polyester polyols. Asexamples of the polyhydric alcohol, ethylene glycol, polyethyleneglycol, tetramethylene glycol, polytetramethylene glycol,1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol,2-methyl-1,8-octanediol, and the like can be given. As examples of thepolybasic acid, phthalic acid, dimer acid, isophthalic acid,terephthalic acid, maleic acid, fumaric acid, adipic acid, sebasic acid,and the like can be given.

These polyester polyol compounds are commercially available under thetrademarks such as MPD/IPA500, MPD/IPA1000, MPD/IPA2000, MPD/TPA500,MPD/TPA1000, MPD/TPA2000, Kurapol A-1010, A-2010, PNA-2000, PNOA-1010,and PNOA-2010 (manufactured by Kuraray Co., Ltd.).

As examples of the polycarbonate polyols, polycarbonate ofpolytetrahydrofuran, poly(hexanediol carbonate), poly(nonanediolcarbonate), poly(3-methyl-1,5-pentamethylene carbonate), and the likecan be given.

As commercially available products of these polycarbonate polyols,DN-980, DN-981 (manufactured by Nippon Polyurethane Industry Co., Ltd.),Priplast 3196, 3190, 2033 (manufactured by Unichema), PNOC-2000,PNOC1000 (manufactured by Kuraray Co., Ltd.), PLACCEL CD220, CD210,CD208, CD205 (manufactured by Daicel Chemical Industries, Ltd.),PC-THF-CD (manufactured by BASF), and the like can be given.

Polycaprolactone diols obtained by reacting e-caprolactone and a diolcompound are given as examples of the polycaprolactone polyols having amelting point of 0° C. or higher. Here, given as examples of the diolcompound are ethylene glycol, polyethylene glycol, polypropylene glycol,polypropylene glycol, tetramethylene glycol, polytetramethylene glycol,1,2-polybutylene glycol, 1,6-hexanediol, neopentyl glycol,1,4-cyclohexanedimethanol, 1,4-butanediol, and the like.

Commercially available products of these polycaprolactone polyolsinclude PLACCEL 240, 230, 230ST, 220, 220ST, 220NP1, 212, 210, 220N,210N, L230AL, L220AL, L220PL, L220PM, L212AL (all manufactured by DaicelChemical Industries, Ltd.), Rauccarb 107 (by Enichem), and the like.

As examples of other polyols used as the component (A), ethylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyoxyethylenebisphenol A ether, polyoxypropylene bisphenol A ether, polyoxyethylenebisphenol F ether, polyoxypropylene bisphenol F ether, and the like canbe given.

As these other polyols, those having a alkylene oxide structure in themolecule, in particular polyether polyols, are preferred. Specifically,polyols containing polytetramethylene glycol and copolymer glycols ofbutyleneoxide and ethyleneoxide are particularly preferred.

The reduced number average molecular weight derived from the hydroxylnumber of these polyols is usually from 50 to 15,000, and preferablyfrom 1,000 to 8,000.

Polypropylene glycol or copolymer glycol of propylene oxide and ethyleneoxide, having a molecular weight between 1,000 and 13,000 and an amountof unsaturation less than 0.01 meq/g, and one or more of these furtherpolyols used to form an oligomer with a copolymeric or polypolymericbackbone with copolymers of the other polyols and mixtures thereof (i.e.glycols a.1 to further polyols a.2) may be present in a ratio 1:5 and5:1, and preferably 1:2 and 2:1.

Given as examples of the polyisocyanate used as the component (B) are2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylenediisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalene diisocyanate,m-phenylene diisocyanate, p-phenylene diisocyanate,3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethanediisocyanate, 3,3′-dimethylphenylene diisocyanate, 4,4′-biphenylenediisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate,methylenebis(4-cyclohexylisocyanate), 2,2,4-trimethylhexamethylenediisocyanate, bis(2-isocyanatethyl)fumarate, 6-isopropyl-1,3-phenyldiisocyanate, 4-diphenylpropane diisocyanate, hydrogenateddiphenylmethane diisocyanate, hydrogenated xylylene diisocyanate,tetramethyl xylylene diisocyanate, lysine isocyanate, and the like.These polyisocyanate compounds may be used either individually or incombinations of two or more. Preferred isocyanates are tolylenedi-isocyanate and most preferred isophorone di-isocyanate, andmethylene-bis(4-cyclohexylisocyanate).

Examples of the hydroxyl group-containing (meth)acrylate used as thecomponent (C), include, (meth)acrylates derived from (meth)acrylic acidand epoxy and (meth)acrylates comprising alkylene oxides, more inparticular, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropylacrylate and2-hydroxy-3-oxyphenyl(meth)acrylate. Acrylate functional groups arepreferred over methacrylates.

The ratio of the polypropylene glycol (A), polyisocyanate (B), andhydroxyl group-containing (meth)acrylate (C) used for preparing theurethane (meth)acrylate is determined so that 1.1 to 3 equivalents of anisocyanate group included in the polyisocyanate and 0.1 to 1.5equivalents of a hydroxyl group included in the hydroxylgroup-containing (meth)acrylate are used for one equivalent of thehydroxyl group included in the glycol.

Part of the compounds containing an ethylenically unsaturated group maybe replaced by compounds having a functional group which can be added toan isocyanate group. As examples of such a compound,γ-mercaptotrimethoxysilane, γ-aminotrimethoxysilane, and the like can begiven. Use of these compounds improves adhesion to substrates such asglass.

In the reaction of these three components, a urethanization catalystsuch as copper naphthenate, cobalt naphthenate, zinc naphthenate,di-n-butyl tin dilaurate, triethylamine, andtriethylenediamine-2-methyltriethyleneamine, is usually used in anamount from 0.01 to 1 wt % of the total amount of the reactant. Thereaction is carried out at a temperature from 10 to 90° C., andpreferably from 30 to 80° C.

The urethane (meth)acrylate thus prepared possesses the moleculeterminal shown by the above formula (1). As examples of the organicgroup shown by R² in the formula (1), alkyl groups such as a methylgroup and an ethyl group, alkoxy groups such as a methoxy group and anethoxy group, and the like can be given. In particular, a hydrogen atomis preferable as R².

The number average molecular weight of the urethane (meth)acrylate usedin the composition of the present invention is preferably in the rangefrom 1200 to 20,000, and more preferably from 2,200 to 10,000. If thenumber average molecular weight of the urethane (meth)acrylate is lessthan 100, the resin composition tends to solidify; on the other hand, ifthe number average molecular weight is larger than 20,000, the viscosityof the composition becomes high, making handling of the compositiondifficult.

The urethane (meth)acrylate is used in an amount from 10 to 90 wt %, andpreferably from 20 to 80 wt %, of the total amount of the resincomposition. When the composition is used as a coating material foroptical fibers, the range from 20 to 80 wt % is particularly preferableto ensure excellent coatability, as well as superior flexibility andlong-term reliability of the cured coating.

In a further embodiment of the invention, the proportion of thepolyurethane (a) thus obtained in the composition is 40-95 wt %, andpreferably 45-85 wt %, in the total amount of the components (a),reactive diluent (b), and amine compound (c).

Polymerizable vinyl monomers such as polymerizable monofunctional vinylmonomers containing one polymerizable vinyl group in the molecule andpolymerizable polyfunctional vinyl monomers containing two or morepolymerizable vinyl groups in the molecule may be added to the liquidcurable resin composition of the present invention.

In a preferred embodiment of the present invention the component (b)used is a mono-functional (meth)acrylate of which the homopolymer has aglass transition temperature of 20° C. or less.

Given as specific examples of the polymerizable monofunctional vinylmonomers are vinyl monomers such as N-vinylpyrrolidone,N-vinylcaprolactam, vinylimidazole, and vinylpyridine; (meth)acrylatescontaining an alicyclic structure such as isobornyl (meth)acrylate,bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl (meth)acrylate, and cyclohexyl(meth)acrylate; benzyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate,acryloylmorpholine, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate,t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate,hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate,isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl(meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl(meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl(meth)acrylate, isostearyl (meth)acrylate, tetrahydrofurfuryl(meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol(meth)acrylate, benzyl(meth)acrylate, phenoxyethyl(meth)acrylate,polyethylene glycol mono(meth)acrylate, polypropylene glycolmono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl(meth)acrylate, methoxypolyethylene glycol (meth)acrylate,methoxypropylene glycol (meth)acrylate, diacetone(meth)acrylamide,isobutoxymethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide,t-octyl(meth)acrylamide, dimethylaminoethyl (meth)acrylate,diethylaminoethyl (meth)acrylate, 7-amino-3,7-dimethyloctyl(meth)acrylate, N,N-diethyl(meth)acrylamide,N,N-dimethylaminopropyl(meth)acrylamide, hydroxy butyl vinyl ether,lauryl vinyl ether, cetyl vinyl ether, 2-ethylhexyl vinyl ether,acrylate monomers shown by the following formulas (1) to (3),

wherein R⁷ is a hydrogen atom or a methyl group, R⁸ is an alkylene grouphaving 2-6, and preferably 2-4 carbon atoms, R⁹is a hydrogen atom or anorganic group containing 1-12 carbon atoms or an aromatic ring, and r isan integer from 0 to 12, and preferably from 1 to 8,

wherein R⁷ is the same as defined above, R¹⁰ is an alkylene group having2-8, and preferably 2-5 carbon atoms, and q is an integer from 1 to 8,and preferably from 1 to 4,

wherein R⁷, R¹⁰, and q are the same as defined above.

As examples of commercially available products of the polymerizablemonofunctional vinyl monomers, Aronix M102, M110, M111, M113, M117(manufactured by Toagosei Co., Ltd.), LA, IBXA, Viscoat #190, #192,#2000 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), LightAcrylate EC-A, PO-A, NP-4EA, NP-8EA, M-600A, HOA-MPL (manufactured byKyoeisha Chemical Co., Ltd.), KAYARAD TC110S, R629, R644 (manufacturedby Nippon Kayaku Co., Ltd.), and the like can be given.

Of these, nonylphenol EO-modified acrylate, lauryl acrylate, andnonylphenol PO-modified acrylate are preferable. The proportion ofmono-functional (meth)acrylate compounds as component (b) (being amonofunctional methacrylate of which the homopolymer has a glasstransition temperature of 20° C. or less) is 3-50 wt %, and preferably5-40 wt %, in the total amount of the components (a), (b), and (c) theamine compound.

Given as examples of the polymerizable polyfunctional vinyl monomers arethe following acrylate compounds: trimethylolpropane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, ethylene glycol di(meth)acrylate,tetraethylene glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate,trimethylolpropanetrioxyethyl (meth)acrylate,tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate,tris(2-hydroxyethyl)isocyanurate di(meth)acrylate,bis(hydroxymethyl)tricyclodecane di(meth)acrylate, di(meth)acrylate of adiol which is an addion compound of ethylene oxide or propylene oxide tobisphenol A, di(meth)acrylate of a diol which is an addition compound ofethylene oxide or propylene oxide to hydrogenated bisphenol A,epoxy(meth)acrylate obtained by the addition of (meth)acrylate todiglycidyl ether of bisphenol A, diacrylate of polyoxyalkylene bisphenolA, and triethylene glycol divinyl ether.

Examples of commercially available products of the polymerizablepolyfunctional vinyl monomers include Yupimer UV SA1002, SA2007(manufactured by Mitsubishi Chemical Corp.), Viscoat #195, #230, #215,#260, #335HP, #295, #300, #700 (manufactured by Osaka Organic ChemicalIndustry Co., Ltd.), Light Acrylate 4EG-A, 9EG-A, NP-A, DCP-A, BP-4EA,BP-4PA, PE-3A, PE-4A, DPE-6A (manufactured by Kyoeisha Chemical Co.,Ltd.), KAYARAD R-604, DPCA-20,-30,-60,-120, HX-620, D-310, D-330(manufactured by Nippon Kayaku Co., Ltd.), Aronix M-208, M-210, M-215,M-220, M-240, M-305, M-309, M-315, M-325 (manufactured by Toagosei Co.,Ltd.), and the like.

These polymerizable vinyl monomers are used in an amount from 10 to 70wt %, and preferably from 15 to 60 wt %, of the total amount of theresin composition. If the amount is less than 10 wt %, the viscosity ofthe composition is so high that coatability is impaired. The amountexceeding 70 wt % may result in not only an increased cure shrinkage,but also insufficient toughness of the cured products.

The liquid curable resin composition of the present invention can becured by heat or radiation. Here, radiation includes infrared radiation,visible rays, ultraviolet radiation, X-rays, electron beams, α-rays,β-rays, γ-rays, and the like. Visible and UV radiation are preferred.

A polymerization initiator can be added when the liquid curable resincomposition of the present invention is cured. Either a heatpolymerization initiator or photo-polymerization initiator can be usedas the polymerization initiator. A photo-polymerization initiator ispreferred.

When the liquid curable resin composition of the present invention iscured by heat, a heat polymerization initiator, usually a peroxide or anazo compound, is used. Specific examples include benzoyl peroxide,t-butyl-oxybenzoate, azobisisobutylonitrile, and the like.

When the liquid curable resin composition of the present invention iscured by radiation, a photo-polymerization initiator is used. Inaddition, a photosensitizer is added as required. Given as examples ofthe photo-polymerization initiator are 1-hydroxycyclohexylphenyl ketone,2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde,fluorene, anthraquinone, triphenylamine, carbazole,3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone,4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether,benzoin ethyl ether, benzyl methyl ketal,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanethone,diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one,2,4,6-trimethylbenzoyldiphenylphosphine oxide,bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide,bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and the like.

Examples of commercially available products of the photo-polymerizationinitiator include IRGACURE 184, 369, 651, 500, 907, CGI1700, 1750, 1850,819, CG24-61, Darocur 1116, 1173 (manufactured by Ciba SpecialtyChemicals Co., Ltd.), Lucirin LR8728 (manufactured by BASF), Ubecryl P36(manufactured by UCB), and the like.

Given as examples of the photosensitizer are triethylamine,diethylamine, N-methyldiethanoleamine, ethanolamine,4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and the like.As commercially available products of the photosensitizer, for example,Ubecryl P102, 103, 104, and 105 (manufactured by UCB) are given.

When both heat and radiation are used to cure the liquid curable resincomposition of the present invention, the foregoing heat polymerizationinitiator and photo-polymerization initiator can be used in combination.The amount of the polymerization initiator used here is in the rangefrom 0.1 to 10 wt %, and preferably from 0.5 to 7 wt %, of the totalamount of the components for the resin composition.

Beside the above-described components, other curable oligomers orpolymers may be added to the liquid curable resin composition of thepresent invention to the extent that the characteristics of the liquidcurable resin composition are not adversely affected.

Such other curable oligomers or polymers include polyester(meth)acrylate, epoxy (meth)acrylate, polyamide (meth)acrylate, siloxanepolymer having a (meth)acryloyloxy group, a reactive polymer obtained byreacting (meth)acrylic acid and a copolymer of glycidyl methacrylate andother polymerizable monomers, and the like.

In a preferred embodiment, an amine compound is added to the liquidcurable resin composition of the present invention to prevent generationof hydrogen gas, which causes transmission loss in the optical fibers.Preferably, the amine is a mono- or dialkyl or mono- or dialkanolaminehaving 2-10 carbon atoms in each alkyl chain. As examples of the aminewhich can be used here, ethanolamine, isopropylamine, isobutylamine,dibutylamine, diethanol amine, diisopropylamine, diethylamine,diethylhexylamine, pentylamine, hexylamine, nonylamine, aniline,methylaniline, dihexylamine, and the like can be given.

Of these compounds, ethanolamine, isopropylamine, isobutylamine,diethylamine, butylamine, and diethanolamine are particularlypreferable. The component (c) may be used either individually or incombinations of two or more.

The amount of this amine compound preferably is such, that the amount ofhydrogen gas generated when the cured product is allowed to stand at100° C. for two days is 2.0 H₂/g or less.

From the viewpoint of ensuring excellent cure speed of the compositionand superior durability of the cured products, the amount of the primaryor secondary amines used in the composition as is 0.01-5 wt %,preferably 0.05-3 wt %, and particularly preferably 0.05-1 wt %, for 100wt % of the total of the components (a), (b), and (c).

In addition to the above-described components, various additives such asantioxidants, UV absorbers, light stabilizers, silane coupling agents,coating surface improvers, heat polymerization inhibitors, levelingagents, surfactants, colorants, preservatives, plasticizers, lubricants,solvents, fillers, aging preventives, and wettability improvers can beused in the liquid curable resin composition of the present invention,as required. Examples of antioxidants include Irganox1010, 1035, 1076,1222 (manufactured by Ciba Specialty Chemicals Co., Ltd.), Antigene P,3C, FR, Sumilizer GA-80 (manufactured by Sumitomo Chemical IndustriesCo., Ltd.), and the like; examples of UV absorbers include Tinuvin P,234, 320, 326, 327, 328, 329, 213 (manufactured by Ciba SpecialtyChemicals Co., Ltd.), Seesorb 102, 103, 110, 501, 202, 712, 704(manufactured by Sypro Chemical Co., Ltd.), and the like; examples oflight stabilizers include Tinuvin 292, 144, 622LD (manufactured by CibaSpecialty Chemicals Co., Ltd.), Sanol LS770 (manufactured by Sankyo Co.,Ltd.), Sumisorb TM-061 (manufactured by Sumitomo Chemical IndustriesCo., Ltd.), and the like; examples of silane coupling agents includeaminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, andmethacryloxypropyltrimethoxysilane, and commercially available productssuch as SH6062, SH6030 (manufactured by Toray-Dow Corning Silicone Co.,Ltd.), and KBE903, KBE603, KBE403 (manufactured by Shin-Etsu ChemicalCo., Ltd.); examples of coating surface improvers include siliconeadditives such as dimethylsiloxane polyether and commercially availableproducts such as DC-57, DC-190 (manufactured by Dow-Corning), SH-28PA,SH-29PA, SH-30PA, SH-190 (manufactured by Toray-Dow Corning SiliconeCo., Ltd.), KF351, KF352, KF353, KF354 (manufactured by Shin-EtsuChemical Co., Ltd.), and L-700, L-7002, L-7500, FK-02490 (manufacturedby Nippon Unicar Co., Ltd.).

The viscosity of the liquid curable resin composition of the presentinvention is usually in the range from 200 to 20,000 cP, and preferablyfrom 2,000 to 15,000.

The radiation-curable compositions of the present invention may beformulated such that the composition after cure has a modulus as low as0.1 MPa and as high as 2,000 MPa or more. Those having a modulus in thelower range, for instance, from 0.1 to 10 MPa, preferably 0.1 to 5 MPa,and more preferably 0.5 to less than 3 MPa are typically suitable forinner primary coatings for fiber optics. In contrast, suitablecompositions for outer primary coatings, inks and matrix materialsgenerally have a modulus of above 50 MPa, with outer primary coatingstending to have a modulus more particularly above 100 up to 1,000 MPaand matrix materials tending to be more particularly between about 50MPa to about 200 MPa for soft matrix materials, and between 200 to about1500 MPa for hard matrix materials. The radiation-curable composition ofthe present invention may be formulated such that the composition aftercure has a Tg between −70° C. and 30° C. The Tg is measured as the peaktan-delta in a DMA curve at 2.5% elongation.

Elongation and tensile strength of these materials can also be optimizeddepending on the design criteria for a particular use. For curedcoatings formed from radiation-curable compositions formulated for useas inner primary coatings on optical fibers, the elongation-at-break istypically greater than 80%, more preferably the elongation-at-break isat least 110%, more preferably at least 150% but not typically higherthan 400%. For coatings formulated for outer primary coatings, inks andmatrix materials the elongation-at-break is typically between 10% and100%, and preferably higher than 30%.

The glass transition temperature (Tg), measured as the peak tan-deltadetermined by dynamic mechanical analysis (DMA), can be optimizeddepending on the particulars of the application. The glass transitiontemperature may be from 10° C. down to −70° C. or lower, more preferablylower than 0° C. for compositions formulated for use as inner primarycoatings and 10° C. to 120° C. or higher, more preferably above 30° C.,for compositions designed for use as outer primary coatings, inks andmatrix materials.

The compositions of the present invention will preferably have a curespeed of 1.0 J/cm² (at 95% of maximum attainable modulus). For an outerprimary coating, ink or matrix material, cure speed is preferably about0.5 J/cm² or less (at 95% of maximum attainable modulus), and morepreferably, about 0.3 J/cm² or less, and even more preferably, about 0.2J/cm² or less.

The cured products obtained by the polymerization of the resincomposition of the present invention are particularly suitable for useas a coating material for optical fibers, optical fiber ribbons, and thelike including primary coatings, secondary coatings, colored secondarycoatings, inks, matrix materials and bundling materials.

EXAMPLES

The present invention will be explained in more detail by way ofexamples, which are not intended to be limiting of the presentinvention.

Example 1, Comparative Examples A-B

The components shown in Table 1 were combined, in the amounts noted(parts by weight), to form different curable compositions. The testsresults for these compositions are also set forth in Table 1.

TABLE 1 Comp. Comp. Ex. 1 Ex. A Ex. B Urethane (meth)acrylate oligomer:(1) H-(I-polypropylene glycol^(A))₂-I-H 70.0 H-(I-polypropyleneglycol^(B))₂-I-H 70.0 H-(I-polypropylene glycol^(C))₂-I-H 70.0 Monomers:Aronix M-113 (ethoxylated 5.5 5.5 5.5 nonylphenol acrylate) Isobornylacrylate 20.5 20.5 20.5 N-vinylcaprolactam 7.0 7.0 7.0 1,6-Hexane dioldiacrylate (HDDA) 2.0 2.0 2.0 Photo-polymerization initiator: LucirinTPO¹ 1.2 1.2 1.2 Additives: Irganox 1035² 0.8 0.8 0.8 Sumisorb 110³ 0.150.15 0.15 SH-6062⁴ 1.0 1.0 1.0 Properties Viscosity (cP @ 25° C.) 3,7003,400 2,800 Young's modulus (Kg/mm²) (a) @ 500 mJ/cm² 0.12 0.17 0.14 (b)@ 10 mJ/cm² 0.05 0.06 0.04 Cure Speed (ratio (b)/(a)) 0.42 0.35 0.29¹(2,4,6-Trimethylbenzoyl Diphenyl Phosphine Oxide) ²(Thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) Hydrocinnamate)³(2-Hydroxy-4-methoxy benzophenone) ⁴(γ-mercaptopropyltrimethoxy silane)

Table Notes: (1) Urethane Oligomer=>represented by the structure

H—(I-propylene glycol)2-I—H,

wherein:

H represents a derivative of Hydroxyethylacrylate,

I represents a derivative of Isophoronediisocyanate and Polypropyleneglycol represents a derivative of one of the following polypropyleneglycol:

^(A)ACCLAIM 4200 unsaturation of 0.003 meq/g;

MW=4,000

^(B) XS-3020C unsaturation of 0.03 meq/g,

MW=3,000

^(C) EXCENOL 3020 unsaturation of 0.09 meq/g

MW=3,000

1. Measurement of Viscosity

The viscosity at 25° C. was measured using a BH8 rotator.

2. Evaluation of Mechanical Characteristics of Xured Products forYoung's Modulus and Cure Speed (Measurement of Modulus of Elasticity)

The liquid curable resin composition was applied on a glass plate usingan applicator bar to produce a coating with a thickness of 5-60 μm. Thecoating was irradiated with ultraviolet radiation under a nitrogenatmosphere at a dose of (a) 500 mJ/cm² and (b) 10 mJ/cm². The cured filmwas peeled off from the glass plate and aged under the conditions of a23° C. room temperature and a 50% relative humidity for 12 hours,thereby obtaining test specimens.

The Young's modulus of the test specimens at 23° C. was measuredaccording to JIS K7113 at a tensile rate of 1 mm/min. The Young'smodulus was calculated from the tensile stress at 2.5% distortion. Theratio ((a)/(b)) of Young's modulus of elasticity of the film cured by(a) 500 mJ/cm² UV irradiation and that of the film cured by (b) 10mJ/cm² UV irradiation was calculated. This ratio was taken as the curespeed with higher ratios representing better curing characteristics(i.e., faster curing).

Examples 2 and 3

Components shown in Table 2 were mixed in the amounts noted (wt %).

Oligomer I is the reaction product of 5.87 wt % TDI, 2.6 wt % of2-hydroxyethylacrylate (HEA) and 91.39 wt %. Acclaim 4200 (Mw: 4000;unsaturation of 0.003 meq/g), catalyst and stabilizer.

Oligomer II is the reaction product of 9.7 wt % IPDI, 3.37 wt % HEA,57.15 wt % Acclaim 4200N and 29.62 wt % Priplast 3190. Priplast 3190 isa polyester polyol with dimer acid from Unichema.

Results are given in Table 3.

TABLE 2 Example 2 Example 3 Oligomer I 68.59 — Oligomer II — 77.10 ENPA7.00 — IDA — 8.50 TriDa 7.00 — Ebecryl III 5.00 — VC 4.00 5.00 SR90034.00 5.00 Lucerine TPO 1.3 1.3 Irgacure 184 1.8 1.8 Irganox 1035 0.3 0.3Silane 1.0 1.0 ENPA: ethoxylated nonylphenol acrylate IDA: isodecylacrylate TriDa: tridecyl acrylate Ebecryl III: ethoxylated aliphaticacrylate from UCB VC: N-vinylcaprolactam SR 9003: propoxylated neopentylglycol diacrylate Silane: γ-mercaptopropyl trimethoxysilane

TABLE 3 Example 2 Example 3 viscosity (mPa.s) 5656 8840 cure speed¹ 0.20.3 (J/cm²) Tensile 0.7 1.7 strength² (MPa) Elongation (%) 229 200Modulus (MPa) 0.7 1.10 Tg (peak tan δ) −51° C. −30° C. E′ (MPa) 1.3 1.4peak water 1.8 1.8 absorption water extraction 0.4 0.4 ¹cure speed: UVradiation at which 95% of the attainable modulus is reached ²mechanicalproperties as in standard DSM Desotech B.V. testing methods

Examples 4 and 5

A reaction vessel equipped with a stirrer was charged with 53.34 g of2,4-tolylene diisocyanate, 150 g of nonylphenol EO-modified (4 mols)acrylate (monofunctional acrylate “Aronix M-113” manufactured byToagosei Co., Ltd.), 0.1 g of 2,6-di-t-butyl-p-cresol, and 0.4 g ofdibutyltin dilaurate. The mixture was cooled with ice to a temperatureof 10° C. or less while stirring. Then, 24.4 g of 2-hydroxyethylacrylate was added while controlling the temperature at 20-30° C. Afterreacting for a further one hour at 35° C., 420.61 g of a ring-openingcopolymer of propylene oxide having a number average molecular weight of2,000 (“ACCLAIM 2200” manufactured by Lyondell., unsaturated groupcontent<0.01 meq/g) was added and the mixture was stirred at 50-60° C.for 5 hours. The reaction was terminated when the amount of the residualisocyanate was 0.1 wt % or less. 58.3 g of M-113, 139.9 g of isobornylacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.),71.4 g of lauryl acrylate (manufactured by Osaka Organic ChemicalIndustry Co., Ltd.), 61.3 g of N-vinylcaprolactam (manufactured by ISP),13.5 g of Lucirine TPO (manufactured by BASF), 3 g of Irganox 1035(manufactured by Ciba Specialty Chemicals Co., Ltd.), and 10 g ofγ-mercaptopropyltrimethoxysilane (“SH6062” manufactured by Toray DowCorning Silicone Co., Ltd.) were added to the resulting mixture ofurethane acrylate. The mixture was stirred at 50° C. for 3 hours toobtain a homogeneous liquid composition. This product is designated as“Example 4”. A homogeneous liquid composition was obtained by adding 1 gof isobutylamine to the Liquid composition of example 4 and stirring themixture for one hour at 50° C. This product is designated as “Example5”.

Examples 6 and 7

A reaction vessel equipped with a stirrer was charged with 53.5 g of2,4-tolylene diisocyanate, 150 g of nonylphenol EO-modified (4 mols)acrylate (monofunctional acrylate “Aronix M-113” manufactured byToagosei Co., Ltd.), 0.1 g of 2,6-di-t-butyl-p-cresol, and 0.4 g ofdibutyltin dilaurate. The mixture was cooled with ice to a temperatureof 10° C. or less while stirring. Then, 24.0 g of 2-hydroxyethylacrylate was added while controlling the temperature at 20-30° C. Afterreacting for a further one hour at 35° C., 203.9 g of a ring-openingcopolymer of propylene oxide and ethylene oxide having a number averagemolecular weight of 2,000 (“ACCLAIM 2220” manufactured by Lyondell.,copolymerization ratio, 90:10, unsaturated group content<0.01 meq/g) and317.0 g of polypropylene glycol with a the number average molecularweight 3,000 (“EXENOL3000” made by Asahi Glass Co., Ltd.) were added andthe mixture was stirred at 50-60° C. for 5 hours. The reaction wasterminated when the amount of the residual isocyanate was 0.1 wt % orless. 70.5 g of M-113, 100.0 g of lauryl acrylate (manufactured by OsakaOrganic Chemical Industry Co., Ltd.), 60.0 g of N-vinylcaprolactam(manufactured by ISP), 15.0 g of Lucirine TPO (manufactured by BASF), 3g of Irganox 1035 (manufactured by Ciba Specialty Chemicals Co., Ltd.)were added to the resulting mixture of urethane acrylate. The mixturewas stirred at 50° C. for 3 hours to obtain a homogeneous liquidcomposition. This product is designated as “Example 6”. 1.5 g ofdiethylamine was added to the Liquid composition of Example 6 andstirred for one hour at 50° C. to obtain a homogeneous liquidcomposition. This product is designated as “Example 7”.

Examples 8 and 9

A reaction vessel equipped with a stirrer was charged with 63.1 g of2,4-tolylene diisocyanate, 0.2 g of 2,6-di-t-butyl-p-cresol, and 500.5 gof a ring-opening copolymer of ethylene oxide and propylene oxide(“ACCLAIM 2220”, copolymerization ratio, 90:10, unsaturated groupcontent<0.01 meq/g). The mixture was cooled with ice to a temperature of10° C. or less while stirring. Then, 0.4 g of dibutyltin dilaurate wasadded to initiate the reaction. The liquid temperature increased to 35°C. After the reaction for two hours at 40° C., 5.0 g ofγ-mercaptopropyltrimethoxysilane (“SH6062” manufactured by TorayDowCorning Co.) was added and the mixture was reacted for a further onehour. Next, 30.7 g of 2-hydroxyethyl acrylate was added and the mixturewas stirred for 5 hours while maintaining the temperature at 50-60° C.The reaction was terminated when the amount of the residual isocyanatewas 0.1 wt % or less. 186.7 g of M-113, 102.1 g of phenol EO-modified (4mols) acrylate (“Aronix M-102” manufactured by Toagosei Co., Ltd.), 55.2g of N-vinylcaprolactam (manufactured by BASF), 13.5 g of Lucirine TPO(manufactured by BASF), and 10 g of Irganox 1035 (manufactured by CibaSpecialty Chemicals Co., Ltd.) were added to the resulting mixture ofurethane acrylate. The mixture was stirred at 50° C. for 3 hours toobtain a homogeneous liquid composition. This product is designated as“Example 8”. 1.0 g of diethylamine was added to the Liquid compositionof example 8 and stirred for one hour at 50° C. to obtain a homogeneousliquid composition. This product is designated as “Example 9”.

Example 10-11

A reaction vessel equipped with a stirrer was charged with 77.9 g ofisophorone diisocyanate, 0.2 g of 2,6-di-t-butyl-p-cresol, and 537.7 gof a ring-opening copolymer of ethylene oxide and propylene oxide(“ACCLAIM 2220”, copolymerization ratio, 90:10, unsaturated groupcontent<0.01 meq/g). The mixture was cooled with ice to a temperature of10° C. or less while stirring. Then, 0.5 g of dibutyltin dilaurate wasadded to initiate the reaction. The liquid temperature increased to 35°C. After the reaction for 3 hours at 40° C., 27.1 g of 2-hydroxyethylacrylate was added and the mixture was stirred for 5 hours whilemaintaining the temperature at 50-60° C. The reaction was terminatedwhen the amount of the residual isocyanate was 0.1 wt % or less. 128.5 gof M-113, 128.5 g of isobornyl acrylate (manufactured by Osaka OrganicChemical Industry Co., Ltd.), 69.2 g of N-vinylcaprolactam (manufacturedby BASF), 12.0 g of Lucirine TPO (manufactured by BASF), 3 g of Irganox1035 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 9.9 g ofγ-mercaptopropyltrimethoxysilane (“SH6062” manufactured by Toray DowCorning Silicone Co., Ltd.) were added to the resulting mixture ofurethane acrylate. The mixture was stirred at 50° C. for 3 hours toobtain a homogeneous liquid composition. This product is designated as“Example 10”. 1.0 g of diethylamine was added to the Liquid compositionof example 10 and stirred for one hour at 50° C. to obtain a homogeneousliquid composition. This product is designated as “Example 11”.

Example 12 and Comparative Example C

A reaction vessel equipped with a stirrer was charged with 67.6 g ofisophorone diisocyanate, 0.2 g of 2,6-di-t-butyl-p-cresol, and 608.9 gof polyoxypropylene glycol (molecular weight=3,000, unsaturated groupcontent=0.12 meq/g). The mixture was cooled with ice to a temperature of10° C. or less while stirring. Then, 0.5 g of dibutyltin dilaurate wasadded to initiate the reaction. The liquid temperature increased to 35°C. After the reaction for 3 hours at 40° C., 23.5 g of 2-hydroxyethylacrylate was added and the mixture was stirred for 5 hours whilemaintaining the temperature at 50-60° C. The reaction was terminatedwhen the amount of the residual isocyanate was 0.1 wt % or less. 55.0 gof M-113, 150.0 g of isobornyl acrylate (manufactured by Osaka OrganicChemical Industry Co., Ltd.), 70.0 g of N-vinylcaprolactam (manufacturedby BASF), 10.0 g of 1,6-hexamethylene glycol diacrylate (“Light Acrylate1.6HX-A” manufactured by Kyoeisha Chemical Co., Ltd. ), 12.0 g ofLucirine TPO (manufactured by BASF), 3 g of Irganox 1035 (manufacturedby Ciba Specialty Chemicals Co., Ltd.), and 10.0 g ofγ-mercaptopropyltrimethoxysilane (“SH6062” manufactured by Toray DowCorning Silicone Co., Ltd.) were added to the resulting mixture ofurethane acrylate. The mixture was stirred at 50° C. for 3 hours toobtain a homogeneous liquid composition. This product is designated as“Comparative example C”. 1.0 g of diethylamine was added to the Liquidcomposition of comparative example C and stirred for one hour at 50° C.to obtain a homogeneous liquid composition. This product is designatedas “Example 12”.

Tests Performed

The liquid curable resin compositions obtained in the above Examples4-12 and Comparative Example C were cured to prepare test specimens,which were submitted to the following evaluations. Results are shown inTable 4.

1. Measurement of Viscosity

The viscosity at 25° C. was measured using a BH8 rotator.

2. Preparation of Test Specimens

The liquid curable resin compositions were applied on glass sheets usingan applicator bar for the preparation of films with a 250 μm thickness.The coatings were cured by irradiation of ultraviolet light at a dose of1 J/cm² in the air. The coatings were allowed to stand for 12 hours ormore at a temperature of 23° C. and a relative humidity of 50%, andsubjected to the following tests.

3. Young's Modulus of Elasticity

The cured films were cut into strips with a width of 6 mm and subjectedto measurement of modulus of elasticity. The drawing rate was 1 mm/minand the bench mark distance was 25 mm. The Young's modulus of elasticitywas calculated by dividing the weight at 2.5% elongation by the crosssection and 0.025.

4. Cure Speed

For the cure speed test, cured films with a thickness of about 60 μmwere prepared by irradiating coatings with UV light at a dose of 10mJ/cm² or 500 mJ/cm². The cure speed was determined as a ratio of theYoung's modulus of the film cured at 500 mJ/cm² to the Young's modulusof the film cured at 10 mJ/cm².

5. Hydrogen Gas Generation

The amount of hydrogen gas generated was measured using films with athickness of 200 μm prepared by irradiation of UV light in paragraph 2above. About 1 g of the film was placed in a sealed glass tube andheated at 100° C. for 2 days. The amount of hydrogen gas generated inthe sealed glass tube was quantitatively measured using gaschromatograph.

Table 4 shows, that the use of a polypropylene glycol with a high amountof unsaturation results in a coating composition with a relatively lowcure speed. The cure speed and the release of hydrogen gas on aging canbe surprisingly improved by using a primary or secondary amine (Example12). It is however preferred to use a polyproylene glycol with a lowamount of unsaturation to improve the cure speed (see e.g. Examples 4,6, 8, and 10, which show better cure speed than Example 12). Thecombined use of a polypropylene glycol with low unsaturation and aprimary or secondary amine improves the cure speed and hydrogen gasgeneration even further.

TABLE 4 Composition No. Example Comp. 4 5 6 7 8 9 10 11 12 Ex CComponent Component (a) 50 50 50 50 62 62 65 65 69.3 69.3 (wt %)Component (b) 28 28 32 32 30 30 13 13 5.4 5.4 (wt %) Component (c) — 0.1— 0.15 — 0.1 — 0.1 0.1 — (wt %) Characteristics Viscosity (cP) 5000 56004500 4900 2500 2900 3100 3700 3200 3300 Young's modulus 0.10 0.12 0.080.10 0.15 0.17 0.10 0.12 0.09 0.08 (kg/mm²) Cure speed* 0.60 0.79 0.580.80 0.80 0.91 0.76 0.89 0.48 0.19 Hydrogen gas 3.0 1.5 4.1 1.3 3.8 0.93.9 1.1 1.8 3.3 (μl/g) *Ratio of the Young's modulus at 10 mJ/cm² to theYoung's modulus at 500 mJ/cm²

What is claimed is:
 1. A curable resin composition for optical fiberscomprising (a) 40-95 wt % of polyurethane prepared by reacting (1) apolypropylene glycol having (i) a molecular weight between 2,000 and8,000; and (ii) an amount of unsaturation of less than 0.01 meq/g; (2) apolyester polyol; (3) polyisocyanate; and (4) (meth)acrylate containinga hydroxyl group; (b) 3-50 wt % of mono-functional (meth)acrylate ofwhich the homopolymer has a glass transition temperature of 20° C. orless, and (c) 0.01-5 wt % of primary or secondary amine compound,wherein wt % is based on the total amount of the components (a), (b),and (c).
 2. A radiation curable resin composition comprising: (1) aurethane (meth)acrylate prepared by reacting (a) a polypropylene glycolhaving (i) a molecular weight between 2,000 and 8,000; and (ii) anamount of unsaturation of less than 0.01 meq/g; (b) polyisocyanate; and(c) (meth)acrylate containing a hydroxyl group; (2) at least onecomponent selected from the group consisting of nonylphenol EO-modifiedacrylate, lauryl acrylate, and nonylphenol PO-modified acrylate; and (3)a poly(meth)acrylate monomer.
 3. The composition of claim 2, whereinsaid polyisocyanate includes tolylene di-isocyanate.
 4. The compositionof claim 2, wherein said composition comprises a silane coupling agent.5. The composition of claim 2, wherein said composition comprises acomponent selected from the group consisting N-vinylpyrrolidone,N-vinylcaprolactam, vinyl imidazole, and vinylpyridin.
 6. Thecomposition of claim 2, wherein said composition comprises propoxylatedneopentyl glycol diacrylate.
 7. The composition of claim 2, wherein saidcomposition comprises a photo-polymerization initiator.
 8. Thecomposition of claim 3, wherein said composition comprises antioxidant.9. A substrate comprising a cured coating obtained by radiation curingthe composition of claim
 2. 10. The substrate according to claim 9,wherein the substrate is (i) a bare optical fiber, (ii) an optical glassfiber coated with a secondary coating, (iii) at least two coated opticalglass fibers, or (iv) at least two ribbons comprising at least twocoated optical glass fibers.
 11. An optical fiber, ribbon, or cablecomprising at least one coating obtained by curing the composition ofclaim
 2. 12. A radiation curable resin composition comprising: (1) aurethane (meth)acrylate prepared by reacting (a) a polypropylene glycolhaving (i) a molecular weight between 2,000 and 8,000; and (ii) anamount of unsaturation of less than 0.01 meq/g; (b) a polyester polyol;(c) polyisocyanate; and (d) (meth)acrylate containing a hydroxyl group;and (2) reactive diluent.
 13. The composition of claim 12, wherein saidpolyester polyol is obtained by reacting polyhydric alcohol withpolybasic acid.
 14. The composition of claim 13, wherein said polybasicacid includes dimer acid.
 15. The composition of claim 12, wherein saidpolyisocyanate includes isophorone diisocyanate.
 16. The composition ofclaim 12, wherein said polyisocyanate includes tolylene di-isocyanate.17. The composition of claim 12, wherein said composition comprises asilane coupling agent.
 18. The composition of claim 12, wherein saidcomposition comprises a component selected from the group consistingN-vinylpyrrolidone, N-vinylcaprolactam, vinyl imidazole, andvinylpyridin.
 19. The composition of claim 12, wherein said compositioncomprises a poly(meth)acrylate monomer.
 20. The composition of claim 12,wherein said composition comprises propoxylated neopentyl glycoldiacrylate.
 21. The composition of claim 12, wherein said compositioncomprises a photo-polymerization initiator.
 22. The composition of claim16, wherein said composition comprises antioxidant.
 23. A substratecomprising a cured coating obtained by radiation curing the compositionof claim
 12. 24. The substrate according to claim 23, wherein thesubstrate is (i) a bare optical fiber, (ii) an optical glass fibercoated with a secondary coating, (iii) at least two coated optical glassfibers, or (iv) at least two ribbons comprising at least two coatedoptical glass fibers.
 25. An optical fiber, ribbon, or cable comprisingat least one coating obtained by curing the composition of claim 12.